Spiral forming

ABSTRACT

Spiral forming methods can be used to join edges of a rolled material along a spiral joint to form conical and/or cylindrical structures. Alignment of the edges of the rolled material can be controlled in a wrapping direction as the material is being joined along the spiral joint to form the structure. By controlling alignment of the edges of the material as the edges of the material are being joined, small corrections can be made over the course of forming the structure facilitating control over geometric tolerances of the resulting spiral formed structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/248,106, filed on Jan. 15, 2019, which is a continuation of U.S.patent application Ser. No. 15/191,841, filed on Jun. 24, 2016 (issuedas U.S. Pat. No. 10,493,509), which claims the benefit of priority ofU.S. Provisional Patent Application No. 62/185,064, filed on Jun. 26,2015, with the entire contents of each of the foregoing applicationshereby incorporated herein by reference.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under NSF Phase II SBIRgrant NSF IIP-1353507, awarded by the National Science Foundation. TheUnited States government has certain rights in this invention.

BACKGROUND

In a spiral forming manufacturing process, a sheet of steel is fed intoa mill and continuously roll-formed into a desired shape. For example,using this technique a cylinder or a conical shape can be formed byfeeding sheets of suitably shaped material into the mill andcontinuously joining the curved, roll-formed material along a spiraledge as the material exits the mill. While a variety of usefulstructures such as steel towers for wind turbines can be fabricatedusing this technique, the process remains susceptible to large-scaledeformation or failure in fabricated structures due to small,accumulating errors in alignment and feed rates.

There remains a need for improved techniques for spiral forming, and inparticular, improved techniques that enable the detection and correctionof misalignments along the joined edge(s) of a spiral formed material.

SUMMARY

Spiral forming methods can be used to join edges of a rolled materialalong a spiral joint to form conical and/or cylindrical structures.Alignment of the edges of the rolled material can be controlled in awrapping direction as the material is being joined along the spiraljoint to form the structure. By controlling alignment of the edges ofthe material as the edges of the material are being joined, smallcorrections can be made over the course of forming the structurefacilitating control over geometric tolerances of the resulting spiralformed structure.

In one aspect, a spiral forming method includes monitoring a first edgeregion of a rolled material, monitoring a second edge region of therolled material, detecting a deviation from a target relationshipbetween the first edge region and the second edge region, adjusting ashape of the first edge region and a shape of the second edge regionrelative to one another to reduce the deviation, and, with the firstedge region and the second edge region adjusted relative to one another,joining the first edge region to the second edge region along the spiraljoint. The second edge region can be adjacent to the first edge regionalong a spiral formed in the material such that the first edge region tothe second edge region are joined along the spiral joint.

In some implementations, monitoring the first edge region and monitoringthe second edge region each includes monitoring the respective edgeregion at a position upstream of joining the first edge region to thesecond edge region along the spiral joint.

In some implementations, monitoring the first edge region and monitoringthe second edge region each includes monitoring the respective edgeregion at a first position along the respective edge region andadjusting the respective edge region at a second position along therespective edge region to reduce the deviation. The first position canbe spatially separated from the second position. For example, the firstposition for monitoring the first edge region and monitoring the secondedge region can be downstream of joining the first edge region to thesecond edge region along the spiral joint.

In certain implementations, detecting the deviation includes detectingwhether the first edge region matches the second edge region to within apredetermined tolerance. If the first edge region and the second edgeregion do not match one another to within the predetermined tolerance,adjusting the shape of the first edge region and the second edge regionrelative to one another can include introducing an out-of-plane gapbetween the first edge region and the second edge region. For example,introducing the out-of-plane gap between the first edge region and thesecond edge region can include wrapping the first edge region at a firstdiameter and wrapping the second edge region at a second diameterdifferent from the first diameter. As an additional or alternativeexample, introducing the out-of-plane gap between the first edge regionand the second edge region can include maintaining a maximumout-of-plane gap until the deviation from the target relationshipbetween the first edge region and the second edge region is no longerdetected. As another additional or alternative example, introducing theout-of-plane gap between the first edge region and the second edgeregion can include maintaining the out-of-plane gap for not more than acomplete circumference of the rolled material. As yet another additionalor alternative example, introducing the out-of-plane gap between thefirst edge region and the second edge region can include sizing theout-of-plane gap to match a predetermined portion of the first edgeregion to a predetermined portion of the second edge region.

In some implementations, adjusting the first edge region and the secondedge region relative to one another includes matching discrete portionsof the first edge region to respective discrete portions of the secondedge region. For example, matching the discrete portions of the firstedge region to the respective discrete portions of the second edgeregion can include matching visual indicia on the first edge region torespective visual indicia of the second edge region. Additionally, oralternatively, the respective discrete portions of the first edge regionand the second edge region can be spaced at regular, discrete intervalsalong the first edge region and the second edge region. As an example,the spacing of the regular, discrete intervals along the first edgeregion can be the same as the spacing of the regular, discrete intervalsalong the second edge region.

In certain implementations, detecting the deviation from the targetrelationship between the first edge region and the second edge regionincludes receiving a manual input corresponding to the detecteddeviation.

In some implementations, at least one of monitoring the first edgeregion and monitoring the second edge region includes receiving, from asurface roller in contact with the rolled material, a rolled distancesignal corresponding to the respective first edge region or second edgeregion. In addition, or in the alternative, at least one of monitoringthe first edge region and monitoring the second edge region can includereceiving, from a magnetic sensor in proximity with the rolled material,a magnetic signal corresponding to the respective first edge region orsecond edge region. Additionally, or alternatively, at least one ofmonitoring the first edge region and monitoring the second edge regionincludes receiving, from an optical sensor directed at the rolledmaterial, an optical signal indicative of the respective first edgeregion or second edge region.

In certain implementations, the spiral extends circumferentially aboutan axis of the rolled material and has an axial dimension along the axisdefined by the rolled material. For example, a radial distance from theaxis to the spiral is substantially constant along the axial dimensionof the rolled material such that the rolled material is substantiallycylindrical. As an additional or alternative example, a radial distancefrom the axis to the spiral can be monotonically varying along the axialdimension of the rolled material such that the rolled material issubstantially conical.

In some implementations, the first edge region is along a first rolledsheet and the second edge region is along a second rolled sheet.

In another aspect, a method includes monitoring discrete portions alonga first edge region of a rolled material, monitoring discrete portionsalong a second edge region of the rolled material opposite the firstedge region along a spiral, determining whether one or more of thediscrete portions along the first edge region is aligned, within apredetermined tolerance, with a corresponding one or more of thediscrete portions along the second edge region along the spiral, andmodifying the rolled material to align the respective discrete portionsalong the first edge region and the second edge region. The rolledmaterial can, for example, include a plurality of sheets of materialjoined end to end.

In certain implementations, the respective discrete portions along thefirst edge region and the second edge region include visual indicia. Atleast one of monitoring the discrete portions along the first edgeregion and monitoring the discrete portions along the second edge regioncan, for example, include receiving a signal indicative of the positionof the visual indicia on the first edge region relative to the positionof the visual indicia on the second edge region.

In some implementations, the respective discrete portions along thefirst edge region and the second edge region are at regularly spacedintervals along the first edge region and the second edge region.

In yet another aspect, a method includes positioning a first edge regionof a rolled material adjacent to a second edge region of the rolledmaterial such that the second edge region is opposite the first edgeregion along a spiral, and introducing an out-of-plane misalignment tothe first edge region relative to an abutting edge of the second edgeregion along the spiral to control alignment, in a rolling direction, ofthe first edge region to the second edge region along the abutting edge.

In certain implementations, introducing the out-of-plane misalignment ofthe first edge region relative to the second edge region along thespiral is based on a targeted change between a first path lengthcorresponding to the first edge region and a second path lengthcorresponding to the second edge region.

In some implementations, introducing the out-of-plane misalignment ofthe first edge region relative to the second edge region along thespiral includes modifying an overall circumference of the rolledmaterial.

In certain implementations, introducing the out-of-plane misalignment ofthe first edge region relative to the second edge region along thespiral includes introducing the out-of-plane misalignment along only aportion of a circumference of the rolled material.

In some implementations, an amount of the out-of-plane misalignment ismaintained below a predetermined threshold.

Implementations can include one or more of the following advantages.

In some implementations, the shape of the first edge region and theshape of the second edge region are adjusted relative to one another toreduce the deviation from a target relationship between the edge regionsof the rolled material. Such adjustments can facilitate, for example,making small corrections to misalignments of the first edge region andthe second edge region. Accordingly, as compared to spiral formingmethods that do not include such adjustments, spiral forming methodsincluding such adjustments can facilitate increased control overgeometric tolerances of the resulting spiral formed structure.

In certain implementations, adjusting the shape of the first edge regionand the shape of the second edge region relative to one another toreduce the deviation includes introducing an out-of-plane gap betweenthe first edge region and the second edge region as the material isbeing rolled. Accordingly, the control of the out-of-plane gap can beused to make small corrections to any detected misalignment with littleto no adverse impact on the throughput of the spiral forming process.

In some implementations, the first edge region and the second edgeregion each include respective visual indicia such that detectingdeviation from a target relationship of the first edge region and thesecond edge region can be based on detecting misalignment of the visualindicia. The visual indicia on the first edge region and the second edgeregion do not require structural modification of the first edge regionor the second edge region and, therefore, do not interfere with thestructural quality of the spiral formed structure. Further, misalignmentof the visual indicia can be readily detected by an observer and/oroptical sensors, thus providing a robust mechanism for detectingmisalignment.

Other aspects, features, and advantages will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of a wind turbine assembly including a taperedtower.

FIG. 2 is a perspective, exploded view of the tapered tower of FIG. 1including conical segments.

FIG. 3 is a perspective view of one of the conical segments of thetapered tower of FIG. 1.

FIG. 4 is a perspective view of a conical segment with misaligned edges.

FIG. 5 is a block diagram of a fabrication system.

FIG. 6 is a schematic representation of a spiral forming process carriedout by the fabrication system of FIG. 5.

FIG. 7 is a schematic representation of an edge pusher system of thefabrication system of FIG. 5.

FIG. 8A is a schematic view of a section of a conical segment in whichvisual indicia along a first edge region are misaligned with visualindicia along a second edge region.

FIG. 8B is a schematic view of a section of a conical segment in whichvisual indicia along a first edge region are aligned with visual indiciaalong a second edge region.

FIG. 9A is a top view of a corrective action for aligning a first edgeportion and a second edge portion of a conical segment through thecontrol of an out-of-plane gap.

FIG. 9B is a side view of the corrective action of 9A.

FIG. 10 is a schematic representation of a geometric relationship of acorrective action for aligning a first edge portion and a second edgeportion of a conical segment through control of an out-of-plane gap.

FIG. 11 is a schematic representation of a geometric relationship of acorrective action for aligning a first edge portion and a second edgeportion of a conical segment through control of an out-of-plane gap.

FIG. 12 is a schematic representation of a geometric relationship of acorrective action for aligning a first edge portion and a second edgeportion of a conical segment through control of an out-of-plane gap.

FIG. 13 is a flowchart of an exemplary method of spiral forming astructure.

FIG. 14 is a flowchart of an exemplary method of spiral forming astructure.

FIG. 15 is a flowchart of an exemplary method of spiral forming astructure.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The embodiments will now be described more fully hereinafter withreference to the accompanying figures, in which preferred embodimentsare shown. The foregoing may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments set forth herein.

All documents mentioned herein are hereby incorporated by reference intheir entirety. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the context. Grammatical conjunctions areintended to express any and all disjunctive and conjunctive combinationsof conjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,”“substantially” or the like, when accompanying a numerical value, are tobe construed as including any deviation as would be appreciated by oneof ordinary skill in the art to operate satisfactorily for an intendedpurpose. Ranges of values and/or numeric values are provided herein asexamples only, and do not constitute a limitation on the scope of thedescribed embodiments. The use of any and all examples or exemplarylanguage (“e.g.,” “such as,” or the like) provided herein, is intendedmerely to better illuminate the embodiments and does not pose alimitation on the scope of the embodiments or the claims. No language inthe specification should be construed as indicating any unclaimedelement as essential to the practice of the disclosed embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “above,” “below,” “up,” “down,” andthe like, are words of convenience and are not to be construed aslimiting terms unless specifically stated.

Spiral forming processes of the present disclosure are described withrespect to forming segments of wind towers. However, this is by way ofexample and should not be understood to limit the presently disclosedprocesses in any way. The spiral forming processes of the presentdisclosure can be used to a variety of useful structures such as, forexample, wind towers, pilings, other structural pieces for civilengineers (e.g., columns), pipelines, spiral ducting, and the like.

Referring to FIG. 1, a wind turbine assembly 10 includes a wind turbine12 supported by a tower 14. The tower 14 has a diameter that decreasesalong the length of the tower 14 so that the top where the wind turbine12 is attached has a smaller diameter than the bottom or base. Theaxially tapering diameter of the tower 14 can be useful, for example,for providing a combination of efficient use of material and structuralstrength to support the loads exerted by or on the wind turbine 12 inthe field. The tower 14 may be fabricated from segments formed using acontinuous spiral forming process in which, as described in greaterdetail below, the rolling of the sheet of material is controlled toalign the edges of the sheet material as the sheet of material is rolledinto shape and joined along a spiral joint to form a conical shape. Whenfabricated in this manner, the structural performance of the tower 14may be further impacted by the alignment of material (e.g., steel) thatis wrapped and joined together to form the axially tapering diameter ofthe tower 14. As described herein, control over the alignment of theedges of the sheet material during a continuous spiral forming processfacilitates the ability to make small corrections, thus reducingalignment errors and improving the strength and geometric accuracy ofthe tower 14.

Referring now to FIG. 2, the tower 14 may include a plurality of conicalsegments 16 joined (e.g., welded) to one another. For example, theconical segments 16 can be fabricated at a mill, according to themethods described herein, and then shipped to the field, where theconical segments 16 can be welded or otherwise mechanically coupled toone another to form the tower 14. While this provides a useful, modularstructure, the tower 14 may instead be formed of a unitary conicalsegment without departing from the scope of the present disclosure.

Each conical segment 16 can have either an actual peak or a virtualpeak. For example, one of the conical segments 16 can be shaped as acone and, therefore, have an actual peak at its apex. Additionally, oralternatively, one or more of the conical segments 16 can be shaped as atruncated structure, such as a frusto-conical structure, and, therefore,have a “virtual peak” at the point at which the taper would eventuallydecrease to zero if the structure were not truncated. Unless otherwisespecified, the methods described herein are applicable to conicalsegments 16 having either an actual peak or a virtual peak.

Referring now to FIG. 3, each conical segment 16 may include a pluralityof sheets 18 joined (e.g., welded) to one another along cross joints 20and along a spiral joint 22. As described in further detail below, thesheets 18 may be joined end-to-end along the cross joints 20 prior torolling the sheets 18 into the conical segment 16. As also described infurther detail below, a first edge region 24 of the end-to-end arrangedsheets 18 may be joined (e.g., welded) to a second edge region 26 of theend-to-end arranged sheets 18 along a spiral joint 22.

Geometrically, the conical segment 16 may define a longitudinal axis “C”and have a height “H,” a top diameter D_(t) along a truncated apexportion 28, and a bottom diameter D_(b) along a base 30. In certainimplementations, the conical segment 16 is a right circular cone, andthe longitudinal axis “C” is a central axis. In such implementations,the tower 14 (FIG. 2) is constructed by aligning the longitudinal axis“C” of each of the conical segments 16 and joining the truncated apexportion 28 of a first one of the conical segments 16 to the base 30 ofanother one of the conical segments 16. Thus, it should be appreciatedthat, in such implementations, the top diameter D_(t) of the truncatedapex portion 28 of first one of the conical segments 16 is substantiallyequal (e.g., to within manufacturing tolerances) to the bottom diameterDb of the base 26.

Each sheet 18 in the conical segment 16 may be trapezoidal and joined toeach of the other sheets 18 such that the cross joints 20 extend alongnon-parallel sides of the respective trapezoid of joined sheets 18.Where each sheet 18 is trapezoidal, wrapping the end-to-end joinedsheets 18 results in a first edge region 24 and a second edge region 26extending along parallel sides of the respective trapezoid of joinedsheets 18 in the shape of a spiral. For suitably shaped and sizedtrapezoids, joining the first edge region 24 to the second edge region26 along the spiral produces the spiral joint 22 and the overall conicalshape of the conical segment 16. Accordingly, as described in greaterdetail below, the accuracy with which the first edge region 24 and thesecond edge region 26 are joined to one another to form the spiral joint22 can be a critical factor in meeting any geometric tolerance and/orstructural quality requirements for a tower.

Each sheet 18 can be, for example, steel or any other material suitablefor spiral forming. Each sheet 18 can be substantially the samethickness (e.g., greater than about 5 mm and less than about 40 mm inthickness for wind tower applications, while other thickness ranges areadditionally or alternatively possible for other applications). Incertain implementations, however, the sheets 18 can have varyingmaterial thickness along the height “H” of the conical segment 16. Suchvarying material thickness can, for example, facilitate efficient use ofmaterial, with more material used in portions of the tower 14 (FIG. 2)that experience larger loads and less material used in portions of thetower 14 that experience smaller loads.

The spiral joint 22 may extend in a spiral which, as used herein,includes a joint that wraps around the circumference of a structurewhile also extending along the length of the structure. For example, theterm spiral is inclusive of any curvilinear shape extending multipletimes around the circumference of a structure while also extending alongthe length of the structure. Accordingly, the use of the term spiral, asused herein, should be understood to include a curve on a conical orcylindrical surface.

The spiral joint 22 may extend circumferentially about the longitudinalaxis “C” such that the radial distance from the spiral joint 22 to thelongitudinal axis “C” is monotonically varying in a direction along thelongitudinal axis “C” such that the rolled sheets 18 form a structurethat narrows as it approaches one end. This may be, for example, alinear taper that forms a substantially conical shape of the conicalsegment 16. Thus, the rate of monotonic variation of the radial distancebetween the spiral joint 22 and the longitudinal axis “C” may be afunction of the height “H”, the top diameter D_(t), and the bottomdiameter D_(b) of the conical segment 16. In addition, or in thealternative, the spiral joint 22 can extend circumferentially about thelongitudinal axis “C” of the conical segment 16, and may vary as theposition along the axis changes.

Referring now to FIGS. 3 and 4, the sheets 18 forming the conicalsegment 16 may be aligned with one another such that there are notsignificant gaps and/or overlap between the sheets 18, and they coupledtogether to form the intended structure. By comparison, the sheets 18′forming the conical segment 16′ may not aligned with one another,resulting in significant gaps between and/or overlap of the sheets 18′.As compared to the conical segment 16′ with more significant gaps and/oroverlap of the sheets 18′, the properly aligned and fitted seams of theconical segment 16 will typically have improved structural qualityand/or will have an increased likelihood of falling within intendedgeometric specifications for a particular application. For at leastthese reasons, it is desirable to control the alignment of the sheets 18to reduce the likelihood of significant gaps and/or overlap, and themethods and systems contemplated herein can advantageously supportimproved alignment by dynamically monitoring and correcting deviationsas they arise during spiral forming.

In spiral forming processes, gaps and/or overlap of the sheets ofmaterial, such as those shown with respect to sheets 18′ of conicalsegment 16′, can generally occur if one wrap of the material is advancedor receded compared to a previous wrap of the material. Accordingly, themethods disclosed herein include detecting deviations from a targetrelationship between the first edge region 24 and the second edge region26, and then taking corrective action based on the detected deviations.For example, this may include adjusting the respective shapes of thefirst edge region 24 and the second edge region 26 relative to oneanother to adjust the relative feed rates and reduce and/or eliminatethe deviation as the spiral forming process progresses to join thesheets 18 to one another to form the conical segment 16. It will beappreciated that the adjacent edges will typically be driven by a commonfeed roll or other mechanism, so it may be difficult to physically drivethe adjacent edges at different rates. However, the relative geometry orpath of the adjacent edges may be manipulated to obtain a difference inpath length travelled by the adjacent edges, thus effectively adjustingthe relative feed rate so that the two edges can be re-aligned asdesired (within practical limits) during fabrication.

Referring now to FIGS. 5-7, a fabrication system 32 may include a stocksource 34, a feed system 36, a curving device 38, an edge pusher system40, a first sensor 41 a, a second sensor 41 b, a joining system 42, anda control system 44. As described in greater detail below, thefabrication system 32 may be operable to fabricate the conical segments16 (FIG. 3) according to the spiral forming methods disclosed herein.The control system 44 may receive signals from the first sensor 41 a andthe second sensor 41 b and the control system 44 may control at leastone of the stock source 34, the feed system 36, the curving device 38,the joining system 42, and the edge pusher system 40. In someimplementations, the control system 44 may control more or fewercomponents of the fabrication system 32, and any combinations thereof.For example, the control system 44 may additionally control a runoutsystem to move formed portions of the conical segment 16 in a directionaway from the curving device 38 and/or the joining system 42. Forclarity of explanation, the operation of the fabrication system 32 andthe methods of spiral forming disclosed herein are described withrespect to the conical segments 16 described above. It should beappreciated, however, that other spiral formed structures (e.g.,substantially cylindrical structures) may also or instead be fabricatedusing these techniques.

The control system 44 may include a processing unit 60 and a storagemedium 62 in communication with the processing unit 60. The processingunit 60 can include one or more processors, and the storage medium 62can be a non-transitory, computer-readable storage medium. The storagemedium 62 may store computer-executable instructions that, when executedby the processing unit 60, cause the system 32 to perform one or more ofthe spiral forming methods described herein. Optionally, the controlsystem 44 can include an input device (e.g., a keyboard, a mouse, and/ora graphical user interface) in communication with the processing unit 60and the storage medium 62 such that the processing unit 60 isadditionally, or alternatively, responsive to input received through theinput device as the processing unit 60 executes one or more of thespiral forming methods described herein.

More generally, the control system 44 may include any processingcircuitry configured to receive sensor signals and responsively controloperation of the fabrication system 32. This may, for example, includededicated circuitry configured to execute processing logic as desired orrequired, or this may include a microcontroller, aproportional-integral-derivative controller, or any other programmableprocess controller. This may also or instead include a general purposemicroprocessor, memory, and related processing circuitry configured bycomputer executable code to perform the various control steps andoperations contemplated herein.

The stock source 34 may include sheets 18 of source material, which canbe stored in a magazine or other suitable dispenser to facilitateselection and loading of the sheets 18 during manufacturing. The sheets18 may be joined (e.g., welded) to one another at cross joints 20 toform a continuous strip 35 of the stock material. Where the sheets 18are trapezoidal, the cross joints 20 may be oblique to a feed direction“F” at which the continuous strip 35 enters the curving device 38. Itshould be appreciated, however, that the cross joints 20 can beperpendicular to the feed direction “F” in implementations in which thesheets 18 are rectangular, such as implementations in which thestructure formed by the fabrication system 32 is substantiallycylindrical.

The sheets 18 may include visual indicia 37, which can be added to thesheets 18 before or after formation of the continuous strip 35. Thevisual indicia 37 can be, for example, spaced at regular intervals(e.g., at each meter) along the continuous strip 35, or at any otherconstant or varying interval(s) useful for detecting variations that canbe corrected as contemplated herein. The visual indicia 37 can be, forexample, tick marks or other similar markings observable by an opticalsensor, a machine vision system, and/or manufacturing personnel.Further, the visual indicia 37 can be permanently applied to the sheets18, e.g., through etching or other permanent marking technique, and/orthe visual indicia may be temporarily applied to the sheets 18 usingchalk, paint, stickers, or the like. While it is specificallycontemplated that the visual indicia 37 can be used for automateddetection of misalignment, it should be appreciated that the visualindicia 37 may also provide a convenient, visual, human-readableindicator of successful alignment when fabrication of a structure hasbeen completed. Further, it should be appreciated that that detectingmisalignment is described using the visual indicia 37 by way of exampleand, as described in greater detail below, other forms of indicia (e.g.,changes in material properties) may be used in addition or as analternative to the visual indicia 37 without departing from the scope ofthe present disclosure.

Referring to FIG. 8A, when the first edge region 24 and the second edgeregion 26 of the continuous strip 35 are misaligned along the spiraljoint 22, such misalignment is detectable and/or observable as acorresponding misalignment of the visual indicia 37 on the first edgeregion 24 with respect to the visual indicia 37 on the second edgeregion 26. Thus, FIG. 8A depicts a case in which misalignment betweenthe first edge region 24 and the second edge region 26 has been allowedto continue, and the corrective processes of the present disclosure havenot been applied.

Referring to FIG. 8B, when the wrap of the first edge region 24 and thesecond edge region 26 of the continuous strip 35 is ideally alignedalong the spiral joint 22, this alignment is also detectable and/orobservable as corresponding alignment of the visual indicia 37 on thefirst edge region 24 relative to the second edge region 26. Accordingly,as described in greater detail below, controlling the degree ofalignment and/or misalignment of the visual indicia 37 of the first edgeregion 24 relative to the visual indicia 37 of the second edge region26, as the spiral joint 22 is being formed, can decrease errors inalignment of the first edge region 24 relative to the second edge region26 along the spiral joint 22.

The distance between visual indicia 37 can be increased or decreased,depending on the amount of control desired over the alignment of thefirst edge region 24 relative to the second edge region 26 and, thus,the amount of control desired over the strength quality and/or geometrictolerance required for a specific application. That is, implementationsin which the visual indicia 37 are spaced at smaller distances from oneanother may offer an increased sensitivity to geometric variations, ascompared to implementations in which the visual indicia 37 are spaced atgreater distances from one another. At the same time, placing visualindicia 37 too close together along an edge may result in measurementambiguity where very large displacements are occurring. In the lattercase, where both high sensitivity and large-scale measurements aredesired, each marking may be uniquely encoded so that relativedisplacement can be referenced to a specific visual indicator on theabutting edge. Thus, as will be appreciated by one of ordinary skill inthe art that the spacing and labeling of the visual indicia 37 may takea variety of forms according to the range of expected deviations and thedesired measurement accuracy.

Referring again to FIGS. 5-7, the feed system 36 may be operable totransport the continuous strip 35 of stock material from the stocksource 34 to and/or through the curving device 38. The feed system 36may include any equipment suitable for moving the continuous strip 35according to traditional techniques. Such equipment can include, forexample, robotic arms, pistons, servo motors, screws, actuators,rollers, drivers, electromagnets, or combinations thereof.

The curving device 38 may impart a controllable degree of curvature tothe continuous strip 35 of material fed into it, preferably withoutimparting in-plane deformation to the metal. The curving device 38 may,for example, include a bank 46 including rollers 48 a, 48 b, 48 cpositioned relative to one another and to the continuous strip 35 toimpart curvature to the continuous strip 35 of material fed through therollers 48 a, 48 b, 48 c. Each roller 48 a, 48 b, 48 c can include, forexample, a plurality of individual rollers independently rotatablerelative to one another and arranged along a respective axis defined bythe respective roller 48 a, 48 b, 48 c.

The joining system 42 may mechanically couple the first edge region 24and the second edge region 26 of the curved continuous strip 35 to oneanother along the spiral joint 22. The joining system 42 can include,for example, a welder that welds the first edge region 24 and the secondedge region 26 to one another along the spiral joint 22 using anysuitable welding technique. A variety of techniques for welding areknown in the art and may be adapted for joining an edge as contemplatedherein. This may, for example, include any welding technique that meltsthe base metal or other material along the spiral joint 22, optionallyalong with a filler material that is added to the joint to improve thestrength of the bond. Conventional welding techniques suitable forstructurally joining metal include, by way of example and notlimitation: gas metal arc welding (GMAW), including metal inert gas(MIG) and/or metal active gas (MAG); submerged arc welding (SAW); laserwelding; and gas tungsten arc welding (also known as tungsten, inert gasor “TIG” welding); and many others. These and any other techniquessuitable for forming a structural bond between the first edge region 24and the second edge region 26 may be adapted for use in a joining system42 as contemplated herein. The mechanical coupling imparted by thejoining system 42 can be, for example, continuous along the spiral joint22 to provide enhanced structural strength of the conical segment 16.The mechanical coupling may also or instead include intermittentcoupling (e.g., at fixed distances) along the spiral joint 22 tofacilitate, for example, faster throughput for applications in whichstructural strength of the conical segment 16 is not a key designconsideration.

The first sensor 41 a may be directed toward the first edge region 24and the second sensor 41 b may be directed toward the second edge region26. The first sensor 41 a and the second sensor 41 b can be, forexample, optical sensors in communication with the control system 44and, in certain implementations, the first sensor 41 a and the secondsensor 41 b may be the same sensor, e.g., where a camera captures animage of a region where the abutting edges come into contact (or nearcontact) prior to structural joining. Additionally, or alternatively,the first sensor 41 a and the second sensor 41 b can be one or morecameras in communication with a machine vision system of the controlsystem 44. The first sensor 41 a and the second sensor 41 b may moregenerally include any sensor or combination of sensors suitable fordetecting visual indicia 37 such as any of those described above thathave been placed along the edges of sheets of material, and morespecifically for detecting relative displacement of the visual indicia37 along the adjacent edges. In another aspect, in addition to or in thealternative to the visual indicia 37, the first sensor 41 a and thesecond sensor 41 b can sense changes to one or more material properties(e.g., a magnetic property) such that the one or more materialproperties can be monitored along each of the adjacent edges duringfabrication. In yet another aspect, visual indicia 37 may be omitted androllers or other sensors may be used to continuously and independentlymeasure linear travel along each of the adjacent edges duringfabrication. However measured, any detected differences in linear travelmay be used as a feedback signal, or to generate a feedback signal,useful for controlling a process as contemplated herein.

The first sensor 41 a and the second sensor 41 b may be orientedrelative to the continuous strip 35 to monitor the respective first edgeregion 24 and the second edge region 26 at a position upstream of thejoining system 42. For example, the first sensor 41 a and the secondsensor 41 b may each detect the visual indicia 37 along the respectivefirst edge region 24 and the second edge region 26 such that, bycomparing the time at which the visual indicia 37 were detected on therespective first edge region 24 and the second edge region 26 as thecontinuous strip 35 moves at a known speed in the feed direction “F”,the control system 44 can detect whether the first edge region 24 andthe second edge region 26 are within an acceptable deviation (e.g.,within a predetermined geometric tolerance) from a target relationship(e.g., exact alignment or alignment to within a predetermined tolerance)between the two adjacent edge regions 24, 26. If the alignment of thevisual indicia 37 of the first edge region 24 with the visual indicia 37of the second edge region 26 deviates beyond the target relationship,the control system 44 can execute corrective action through, forexample, control of the edge pusher system 40 that is positionedupstream of the joining system 42.

As shown in FIG. 7, the edge pusher system 40 may include a first pusher50 a and a second pusher 50 b. The first pusher 50 a may be disposedalong an inner surface 51 a of the continuous strip 35 of material, ator near a position in the fabrication system 32 where the continuousstrip 35 of material has been curved into the conical segment 16, butnot yet joined to an adjacent edge. The second pusher 50 b may bedisposed in a complementary position along an outer surface 51 b of thecontinuous strip 35 of material, also at or near a position in thefabrication system 32 where the continuous strip 35 of material has beencurved to form the conical segment 16 but not yet joined. The firstpusher 50 a and the second pusher 50 b may cooperate to controllablyapply normal forces to the plane of a sheet of material to adjust an outof plane alignment of a first edge 72 relative to a second edge 74 alongthe spiral joint. For example, the first pusher 50 a and the secondpusher 50 b may exert normal forces on the curved sheet at or near alocation where the first edge 72 of the curved sheet converges with asecond edge 74, which is also curved, as the two edges 72, 74 cometogether for welding or other joining. While the edge pusher system 40is described herein as including the first pusher 50 a and the secondpusher 50 b, the edge pusher system 40 can include fewer or a greaternumber of pushers, or any other configuration or mechanisms suitable forcontrolling a planar alignment of two sheets of material along aconverging edge in a manner that permits control of an out of —planeoffset between the two sheets. Additionally, or alternatively, any otherconfiguration or combination of configurations suitable for exertingforces on the continuous strip 35 of material to move the first edgeregion 24 and the second edge region 26 relative to one another arewithin the scope of the present disclosure.

The first pusher 50 a and the second pusher 50 b can each include aroller 52 and an actuator 54 mechanically coupled to the roller 52. Theroller 52 of the first pusher 50 a may be in rolling contact with theinner surface 51 a of the continuous strip 35 of material, and theroller 52 of the second pusher 50 b may be in rolling contact with theouter surface 51 b of the continuous strip 35 of material. Morespecifically, each roller 52 may be controllably moved by an actuator 54so that, where planar alignment of the edges 72, 74 is to be adjusted,it moves the material in a desired direction. In general, each actuator54 may be actuatable to move a respective one of the rollers 52 in adirection perpendicular to the respective edge 72, 74 that is not beingmoved such that movement of each actuator 54 moves the edges 72, 74relative to one another.

Further, one or more of the actuators 54 may be in electricalcommunication with the control system 44 such that the control system 44can control the position of one or more of the actuators 54 to controlthe offset imparted by the rollers 52 on the continuous strip 35 ofmaterial. For example, the first pusher 50 a can push down on the innersurface 51 a of the continuous strip 35 while the control system 44controls the position of the actuator 54 of the second pusher 52 brelative to the outer surface 51 b of the continuous strip. Morespecifically, the first pusher 50 a can create a counterforce tomaintain the continuous strip 35 in contact with the roller 52 of thesecond pusher 50 b while the second pusher 50 a is movable in adirection perpendicular to the continuous strip 35 to set the positionfor the continuous strip 35. Thus, it should be appreciated that thisexemplary cooperation between the first pusher 51 a and the secondpusher 51 b can facilitate moving the edges 72, 74 relative to oneanother as part of any one or more of the corrective actions describedherein to control an out-of-plane gap 56 between the first edge region24 and the second edge region 26

The actuators 54 can for example include a motor and screw, a screwjack,or other similar mechanisms. In implementations in which the firstpusher 52 a pushes down on the inner surface 51 a, the actuator 54 can,in addition or in the alternative, include any one or more actuationmechanisms suitable for generating this downward force on the continuousstrip 35, including, by way of non-limiting example, a mechanicalspring, pneumatic piston, pneumatic spring, and combinations thereof. Byway of further non-limiting example, it should be appreciated that theweight of the continuous strip 35 and any section of spiral formedmaterial attached to the continuous strip 35 can, in certain instances,generate downward forces for maintaining contact between the continuousstrip 35 and the roller 52 of the second pusher 50 b. In such instances,if the weight is sufficient to maintain contact between the continuousstrip 35 and the roller 52 of the second pusher 52 b, a single pusher(e.g., pusher 52 b) may be used to move the edges 72, 74 relative to oneanother while the force of gravity maintains the continuous strip 35 incontact with the roller 52 of the second pusher.

While each pusher 50 a, 50 b has been described as having a singleroller 52, other configurations are additionally or alternativelypossible. For example, one or both of the pushers 50 a, 50 b can includea pair of rollers on a rocker. This can, for example, facilitatedistributing the pushing force and reduce the likelihood of local damageto the sheet in applications that require higher push forces.

The edge pusher system 40 may include a gap sensor 58 in communicationwith the control system 44 and directed toward the first edge region 24and the second edge region 26 to measure the out-of-plane gap 56, and/orto provide a signal indicative of the individual or relative positionsof the edge regions 24, 26. The gap sensor 58 can include an opticalsensor, a machine vision sensor, a contact sensor or any sensor orcombination of sensors using, e.g., optical, mechanical, acoustic,electromagnetic, or other forces to detect a relative alignment betweenthe edge regions 24, 26.

The control system 44 may receive, from the first sensor 41 a and fromthe second sensor 41 b, respective signals indicative of the position ofthe visual indicia 37 within the first edge region 24 and the positionof visual indicia 37 within the second edge region 26. Based on thesignals received from the first sensor 41 a and from the second sensor41 b, the control system 44 can detect whether the visual indicia 37along the monitored portion of the first edge region 24 and the visualindicia 37 along the monitored portion of the second edge region 26deviate from a target relationship with one another. In certainimplementations, the control system 44 also receives a signal from thegap sensor 58. Based on the detected deviation of the first edge region24 and the second edge region from a target relationship with oneanother and, optionally, the signal received from the gap sensor 58, thecontrol system 44 can adjust the out-of-plane gap 56 between the firstedge region 24 and the second edge portion 26. For example, the controlsystem 44 can control the wrap diameter of the first edge region 24relative to the wrap diameter of the second edge region 26 throughcontrolling the first pusher 50 a and/or the second pusher 50 b of theedge pusher system 40.

FIGS. 9A-9B are schematic representations of techniques for controllingthe out-of-plane gap 56 to align visual indicia 37 of the first edgeregion 24 with corresponding visual indicia 37 of the second edge regionto maintain a target relationship between the first edge region 24 andthe second edge region 26. FIG. 9A corresponds to a top view of thecorrective action to align the first edge region 24 and the second edgeregion 26 relative to one another. FIG. 9B is a side view of the samecorrective action shown in FIG. 9A. As shown in FIGS. 9A-9B, a detecteddeviation L exists between the visual indicia 37 at area A, which cancorrespond to portions of the first edge region 24 and the second edgeregion 26 monitored by the first sensor 41 a and the second sensor 41 b,as shown for example in FIGS. 5-6.

Through one or more corrective actions, such as the corrective actionsdescribed with respect to FIGS. 10-12 below, a control system (such asany of the control systems described herein) can move the first edgeregion 24 and the second edge region 26 relative to one another by, forexample, controlling an edge pusher system (such as any of the edgepusher systems described herein) such that the respective visual indicia37 of the first edge region 24 and the second edge region 26 move intoalignment with one another when the adjacent sheets of material reacharea B. In the description of each of the corrective actions thatfollows, the first edge region 24 is leading the second edge region 26such that the corrective action is applied to the first edge region 24to make the first edge region 24 move along a longer path than theadjacent edge while both edges moving along an ideal spiral jointbetween the two. This may be continued with the first edge region 24following a longer path relative to the second edge region 26 until therespective visual indicia 37 within the first edge region 24 and thesecond edge region 26 are once again aligned. It should be appreciatedthat this convention is used for the sake of explanation and that thecorrective actions described herein can include any combination ofmovement of the first edge region 24 and the second edge region 26relative to one another. For example, the corrective actions can also orinstead be applied to the second edge region 26 in instances in whichthe second edge region 26 leads the first edge region 24. As anotherexample, the corrective actions can also or instead be applied to eitherthe first edge region 24 or the second edge region 26, irrespective ofwhich edge region is leading, given that applying a corrective action tomake one edge region take a longer path can produce the same result asmaking the other edge region take a shorter path. Further, it should beappreciated that the corrective actions can be applied to the first edgeregion 24 and/or to the second edge region 26 of the same sheet 18, suchas when the sheet 18 is spiral formed with a diameter small enough towrap the sheet 18 onto itself.

Referring to FIG. 10, the respective visual indicia 37 of the first edgeregion 24 and the second edge region 26 can be brought into alignmentwith one another by, for example, changing the radius of curvature ofthe first edge region 24 relative to the radius of curvature of thesecond edge region 26 over a correction angle θ to control anout-of-plane gap 56, which effectively results in wrapping the sheet 18corresponding to the first edge region 24 at a radius of curvaturedifferent than that of the sheet 18 corresponding to the second edgeregion 26. The result is that, over the correction angle θ, the lengthof one of the first edge region 24 and the second edge region 26 isshorter than the other one of the first edge region 24 and the secondedge region 26. This difference in length can bring the respectivevisual indicia 37 of the first edge region 24 and the second edge region26 into alignment with one another at area B. It will be understood thatthis technique is advantageously bi-directional. That is, the controllededge—the edge with a varying radius of curvature—may be controlled toincrease or decrease its length relative to the non-varying edge, thusfacilitating re-alignment in either direction as necessary.

The magnitude of the detected deviation L is the amount of the alignmenterror to be corrected and may be expressed as follows for a correctiveaction in which a radius of curvature of the first edge region 24 is tobe changed relative to the radius of curvature of the second edge region26:

L=R _(N)θ_(N) −R _(G)θ_(G)  Eq. 1

where:

-   -   R_(N)=radius of curvature of the second edge region 26, which is        equal to the nominal tube radius;    -   θ_(N)=wrap angle over which to correct the detected deviation L;    -   R_(G)=radius of curvature imparted on the first edge region 24;        and    -   θ_(G)=equivalent wrap angle for the curve of the first edge        region 24.

In general, R_(N) is a known parameter dictated by the design of thestructure being spiral formed, and R_(G) and θ_(N) are determined basedon a maximum permitted linear magnitude d of the out-of-plane gap 56, asillustrated by a maximum gap 57 in FIG. 9B. For example, the magnitude dof the out-of-plane gap 56 may be limited by a product specification(e.g., a variability specified by the end user) or the magnitude d maybe established by physical limitations on a welding process or othertechnique used to join the edges. R_(G) and θ_(G) are related to oneanother as follows:

$\begin{matrix}{{\sin\mspace{11mu}\left( \frac{\theta_{G}}{2} \right)} = {\frac{R_{N}}{R_{G}}\sin\mspace{11mu}\left( \frac{\theta_{N}}{2} \right)}} & {{Eq}.\mspace{11mu} 2}\end{matrix}$

The magnitude d of the out-of-plane gap is related to these parametersby:

$\begin{matrix}{d = {{R_{N}\left( {1 - {\cos\mspace{14mu}\left( \frac{\theta_{N}}{2} \right)}} \right)} + {R_{G}\left( {{\cos\mspace{14mu}\left( \frac{\theta_{G}}{2} \right)} - 1} \right)}}} & {{Eq}.\mspace{11mu} 3}\end{matrix}$

Based on this relationship, limits for R_(G) and θ_(G) can be determinedthrough Eq. 2 and Eq. 3 when the maximum permitted linear magnitude d ofthe out-of-plane gap 56 is specified.

Referring to FIG. 11, as an additional or alternative example, therespective visual indicia 37 of the first edge region 24 and the secondedge region 26 can be brought into alignment with one another byapplying a step change in radius to the first edge region 24 and thenmaintaining the respective radius of curvature for each edge. In thisembodiment, a magnitude d2 of the out-of-plane gap 56 is maintaineduntil the misalignment of the respective visual indicia 37 of the firstedge region 24 and the second edge region 26 is resolved to within anacceptable degree of alignment. For this type of corrective action, themagnitude of the detected deviation L that is being corrected may beexpressed as follows:

L=R _(N2)η₂−(2L _(T)+(R _(N2) −d ₂)θ₂)  Eq. 4

where:

-   -   L_(T)=a transition length    -   R_(N2)=radius of curvature of the second edge region 26, which        is equal to the nominal tube radius; and    -   θ₂=wrap angle over which to correct the detected deviation L.        The transition length L_(T) (not shown in FIG. 11) accounts for        the finite length required to impart the desired out-of-plane        gap 56 when the change is initiated, and to remove the        out-of-plane gap 56 when the edges are re-aligned and the        adjustment is to be terminated. The magnitude of L_(T) is        dependent on the shape of the transition region and depends, for        example, on physical or practical limitations imposed by the        material being used, the actuators, the control system and other        hardware. In general, however, the longer the path over which        the alignment is corrected the smaller the effect of the        transition area. For a given value of the maximum permitted        linear magnitude d of the out-of-plane gap 56, the wrap angle        over which the error is resolved is expressed as follows:

$\begin{matrix}{\theta_{2} = \frac{L + {2L_{T}}}{d_{2}}} & {{Eq}.\mspace{11mu} 5}\end{matrix}$

Referring to FIG. 12, as an additional or alternative example, therespective visual indicia 37 of the first edge region 24 and the secondedge region 26 can be brought into alignment with one another byimparting an oscillation to one of the first edge region 24 or thesecond edge region 26 while the other one of the first edge region 24 orthe second edge region 26 is maintained at the nominal radius of thestructure being spiral formed, e.g., along an idealized spiral joint forthe structure. This oscillation imparts a longer relative path to one ofthe edge regions so that the other edge can catch up to a realignedstate as both sheets traverse the idealized spiral joint.

At each point along the oscillating segment, when the oscillation is inthe form of a sine wave, the position (radius) of the oscillating sheet,R_(s), can be calculated by:

$\begin{matrix}{R_{s} = {R_{N3} + {A_{s}\sin\mspace{11mu}\left( {2\pi\frac{\theta}{\lambda_{s}}} \right)}}} & {{Eq}.\mspace{11mu} 6}\end{matrix}$

where:

-   -   θ=angular distance along the path;    -   R_(N3)=nominal radius of curvature of the second edge region,        which is equal to the nominal tube radius    -   λ_(s)=angular wavelength of sine wave    -   A_(s)=amplitude of sine wave        Then, the length of the oscillating segment, L_(s), can be        calculated by:

$\begin{matrix}{L_{s} = {\int_{\theta A}^{\theta B}{\sqrt{\begin{matrix}{R_{N3}^{2} + A_{s}^{2} + {2R_{N3}A_{s}\sin\;({\omega\theta})} +} \\{A_{s}^{2}\;\cos^{2}\;({\omega\theta})\left( {\omega^{2} - 1} \right)}\end{matrix}}\mspace{14mu}{where}\text{:}}}} & {{Eq}.\mspace{11mu} 7} \\{\omega = \frac{2\pi}{\lambda_{s}}} & {{Eq}.\mspace{11mu} 8}\end{matrix}$

and θ_(A), θ_(B) are the wrap angles at which the oscillation begins andends, respectively. Then the alignment error that is corrected is:

L=R _(N3)Θ₃ −L _(s)  Eq. 9

In general, a shorter wavelength and a larger amplitude allow thealignment error, L, to be corrected over a shorter distance. Thewavelength and the amplitude may in general by limited by manufacturingcapabilities, materials, product specifications, or any other relevantcriteria.

Referring now to FIG. 13, a flowchart of an exemplary method 130 ofspiral forming a structure is shown. It should be appreciated that themethod 130 can be carried out, for example, by any of the fabricationsystems described herein to form any of the structures described herein,including but not limited to a cylinder, a cone or a frusto-conicalstructure or segment. For example, one or more steps in the exemplarymethod 130 can be carried out by a processing unit of a control system(e.g., the processing unit 60 of the control system 44 in FIG. 5).Additionally, or alternatively, one or more steps in the exemplarymethod 130 can be carried out by an operator providing inputs (e.g.,through a keyboard, a mouse, and/or a graphical user interface) to acontrol system such as the control system 44 of FIG. 5.

The exemplary method 130 includes monitoring 132 a a first edge regionof a rolled material, monitoring 132 b a second edge region of therolled material, detecting 134 a deviation from a target relationshipbetween the first edge region and the second edge region, adjusting 136a shape of the first edge region and a shape of the second edge regionrelative to one another to reduce the deviation, and joining 138 thefirst edge region to the second edge region. It should be appreciatedthat, if deviation is not detected 134, the first edge region and thesecond edge region can be jointed 138 together without adjusting 136 theshape of the first edge region and the shape of the second edge regionrelative to one another. The second edge region is adjacent to andjoined to the first edge region along a spiral joint formed in therolled material. The first edge region can be along a first rolledsheet, and the second edge region can be along a second rolled sheetwhich, in certain implementations, is joined to an end of the firstrolled sheet.

The spiral can extend circumferentially about an axis of the rolledmaterial, generally with a radius greater than a thickness of the rolledmaterial. In some implementations, a radial distance from the axis tothe spiral is substantially constant along the axial dimension of therolled material such that the material is cylindrical. In someimplementations, a radial distance from the axis to the spiral changesat a constant rate such that the rolled material is conical. Otheruseful structures may be formed with other monotonically decreasingchanges in radius. It should be appreciated that strict geometricprecision is not generally required, and the resulting shape of thespiral formed structure may be substantially cylindrical or conical,e.g., to within manufacturing tolerances or other specifications.

Monitoring 132 a the first edge region of the rolled material andmonitoring 132 b the second edge region of the rolled material caninclude receiving signals from one or more sensors detecting respectivevisual indicia on the first edge region and the second edge region. Theone or more sensors for monitoring 132 a the first edge region andmonitoring 132 b the second edge region can be any of the types ofsensors described herein. Additionally, alternatively, monitoring 132 athe first edge region of the rolled material and monitoring 132 b thesecond edge region of the rolled material can include receiving an inputfrom an input device operated by an operator observing the first edgeregion and the second edge region.

Monitoring 132 a the first edge region and monitoring 132 b the secondedge region can be done, for example, at a position upstream of joining138 the first edge region to the second edge region of the spiral joint.In such implementations, a detected misalignment at a given positionalong the first edge region and the second edge region can be correctedbefore joining 138 the first edge region to the second edge region ofthe spiral joint.

Additionally, or alternatively, monitoring 132 a the first edge regionand monitoring 132 b the second edge region can be done at a firstposition along the respective edge regions, and the shape of the firstedge region and the shape of the second edge region can be adjusted 136at a second position along the respective edge regions. In suchimplementations, the first position is spatially separated from thesecond edge position. For example, monitoring 132 a the first edgeregion and monitoring 132 b the second edge region can be done at afirst position downstream of joining 138 the first edge region and thesecond edge region while the shape of the first edge region and theshape of the second edge region can be adjusted 136 at a second positionupstream of joining 138 the first edge region and the second edgeregion. In such implementations, the adjustment 136 at the secondposition is based on the monitoring 132 a, 132 b at the first position.

In certain implementations, monitoring 132 a the first edge regionand/or monitoring 132 b the second edge region includes monitoringdiscrete portions of each respective edge region. For example, each edgeregion can have visual indicia, such as tick marks, that are monitoredfor alignment with one another. Such monitoring of alignment of visualindicia along the first edge region and the second edge region can beperformed semi-automatically, and may for example include receivinginput from an operator regarding the level of alignment based uponvisual inspection. Additionally, or alternatively, such monitoring ofalignment of visual indicia along the first edge region and the secondedge region can include automatically monitoring the alignment, such asby receiving, from an optical sensor directed at the rolled material, anoptical signal indicative of the respective edge region or second edgeregion (e.g., indicative of the position of visual indicia along eachedge region). As another additional or alternative example, the firstedge region and the second edge region can include discrete portionswith different optical, mechanical, or magnetic properties that differfrom those of the bulk of the sheet material, and monitoring can includedetecting corresponding changes as material passes by sensors during afabrication process.

Monitoring 132 a the first edge region and/or monitoring 132 b thesecond edge region may also or instead include continuously monitoringeach respective edge region, such as by monitoring a surface roller incontact with the rolled material, a rolled distance signal correspondingto the respective first edge region or second edge region.

More generally, it should be appreciated that any of the sensorsdescribed herein, alone or in combination with one another, can be usedto monitor 132 a the first edge and/or monitor 132 b the second edgewithout departing from the scope of this disclosure. Similarly,monitoring may generally include marking the material at predeterminedintervals with suitable visual or other indicia to facilitatemonitoring. This may, for example, include etching, painting, inking,magnetizing, applying stickers, and so forth. The intervals may be fixedintervals, or the intervals may vary, e.g., according to the desiredsensitivity of measurements.

Detecting 134 the deviation from the target relationship between thefirst edge region and the second edge region can include comparing themonitored first edge region to the monitored second edge region and/orto a standard. For example, detecting 134 the deviation from the targetrelationship can include detecting whether the first edge region matchesthe second edge region to within a predetermined tolerance (e.g., aspecified manufacturing tolerance). In certain implementations, trackingindicia can be marked on the first edge region and/or the second edgeregion such that detecting 134 the deviation from the targetrelationship includes detecting whether a location of the indicia infirst edge region matches a location of the indicia in the second edgeregion to within the desired tolerance.

Detecting 134 the deviation from the target relationship between thefirst edge region and the second edge region can be carried out by orwith the assistance of a processing unit of a control system such as anyof the control systems described herein. While this may include fullyautomated monitoring and correction, e.g., using the techniquesdiscussed above, this may also include semi-automated techniques. Forexample, detecting 134 the deviation from the target relationshipbetween the first edge region and the second edge region can includereceiving a manual input from an operator indicating the presence and/ordegree of the detected deviation. In one embodiment, the operator canvisually compare a signal received from a monitored 132 a first edgeregion and a monitored 132 b second edge region and provide a manualinput to the control system if the operator determines that the firstedge region and the second edge region are misaligned. The manual inputfrom the operator can, for example, initiate a step of adjusting 136 theshape of the first edge region and the second edge region relative toone another using any of the techniques described herein.

Adjusting 136 the shape of the first edge region and the second edgeregion may include carrying out one or more of the corrective actionsdescribed herein. For example, adjusting 136 the shape of the first edgeregion and the second edge region relative to one another may includecontrolling an out-of-plane gap between the first edge region and thesecond edge region if the first edge region and the second edge regiondo not match one another to within a predetermined tolerance. Theout-of-plane gap can be controlled, for example, by wrapping the firstedge region at a first diameter and wrapping the second edge region at asecond diameter different from the first diameter. Additionally, oralternatively, controlling the out-of-plane gap between the first edgeregion and the second edge region can include maintaining a maximumout-of-plane gap until the deviation from the target relationshipbetween the first edge region and the second edge region is no longerdetected. For example, the corrective out-of-plane gap can be maintainedfor not more than a complete circumference of the rolled material suchthat misalignment is corrected quickly. As another non-exclusiveexample, the out-of-plane gap can be sized to match a predeterminedportion of the first edge region to a predetermined portion of thesecond edge region such that misalignment is resolved at a predeterminedposition.

In some implementations, adjusting 136 the shape of the first edgeregion and the second edge region relative to one another includesmatching discrete portions of the first edge region to respectiveportions of the second edge region. In general, where the first edgeregion and the second edge region each include respective visual indiciaalong discrete portions of the respective edge regions, adjusting 136the shape of the first edge region and the second edge region relativeto one another can include matching the discrete portions of the edgeregions to one another. The discrete portions can be, for example,spaced at regular intervals along the first edge region and along thesame or different regular intervals along the second edge region suchthat the first edge region and the second edge region are adjusted 136relative to one another at least at the regular intervals marked by therespective visual indicia along the first edge region and along thesecond edge region, and in a manner that moves the visual indicia backinto alignment as necessary.

Joining 138 the first edge region to the second edge region can includewelding the first edge region to the second edge region using anysuitable welding technique or other process suitable for structurallyjoining sheets of steel or other building material. In suchimplementations, a welding unit may remain stationary to direct weldingenergy to a fixed point while the first edge region and the second edgeregion rotate as part of the spiral forming process.

Referring now to FIG. 14, a flowchart of another exemplary method 140 ofspiral forming a structure is shown. The method 140 can be carried out,for example, by any of the fabrication systems described herein to forma structure such as a conical segment. For example, one or more steps inthe exemplary method 140 can be carried out by a processing unit of acontrol system. Additionally, or alternatively, one or more steps in theexemplary method 140 can be carried out by an operator providing inputs(e.g., through a keyboard, a mouse, and/or a graphical user interface)to a control system.

The exemplary method 140 includes monitoring 142 a discrete portionsalong a first edge region of a rolled material (e.g., a plurality ofsheets joined end to end), monitoring 142 b discrete portions along asecond edge region of a rolled material, determining 144 whether one ormore of the discrete portions along the first edge region is aligned,within a predetermined tolerance, with a corresponding one or more ofthe discrete portions along the second edge region along a spiral, andmodifying 146 the rolled material to align the respective discreteportions along the first edge region and the second edge region. Thesecond edge region is opposite the first edge region along a spiraljoint, and modifying 146 the rolled material to align the respectivediscrete portions of the first edge region and the second edge regioncan include any one or more of the corrective actions described herein,or any other physical modification of the rolled material that can beusefully employed to correctively adjust the abutting edge regions toaddress any misalignment that is detected. Further, the discreteportions of the first edge region and the second edge region can bedemarcated using any of the marking or other detection techniquesdescribed herein.

Referring now to FIG. 15, a flowchart of yet another exemplary method150 of spiral forming a structure is shown. The method 150 can becarried out by the any of the fabrication systems described herein toform a structure such as the conical segment. For example, one or moresteps in the exemplary method 150 can be carried out by a processingunit of a control system. Additionally, or alternatively, one or moresteps in the exemplary method 150 can be carried out by an operatorproviding inputs (e.g., through a keyboard, a mouse, and/or a graphicaluser interface) to a control system.

The exemplary method 150 includes positioning 152 a first edge region ofa rolled material adjacent to a second edge region of the rolledmaterial and introducing 154 an out-of-plane misalignment to the firstedge region relative to an abutting edge of the second edge region. Thesecond edge region is positioned 152 opposite the first edge regionalong a spiral according to any one or more of the methods describedherein. In general, the spiral may follow a path of a spiral joint foran idealized fabrication process. The out-of-plane misalignment may beintroduced 154 along the spiral to control an alignment, in the rollingdirection, of the first edge region to the second edge region along theabutting edge such that the two edge regions are adjusted whilesubstantially maintaining the intended path for the spiral joint. Thecontrol 154 of this out-of-plane misalignment can be carried outaccording to any one or more of the corrective actions described herein.

While certain embodiments have been described, other embodiments areadditionally or alternatively possible.

For example, while joining a first edge region to a second edge regionhas been described as including welding, other methods of joining edgeregions to one another are additionally or alternatively possible.Examples of such other methods include adhesive bonding, spot welding,seam locking, and/or mechanical fastening with bolts, rivets and thelike, as well as combinations of the foregoing.

As another example, to the extent that one or more of the exemplarymethods described herein have been described as being carried out by acontrol system, it should be appreciated that, in addition or in thealternative, one or more aspects of the exemplary methods describedherein can be carried out by a human operator. For example, one or morecorrective actions of the exemplary methods described herein can becarried out by an operator providing direct inputs (e.g., through ajoystick) to one or more mechanical actuators such as those of the edgepusher system 40 of FIG. 5.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable forthe control, data acquisition, and data processing described herein.This includes realization in one or more microprocessors,microcontrollers, embedded microcontrollers, programmable digital signalprocessors or other programmable devices or processing circuitry, alongwith internal and/or external memory. This may also, or instead, includeone or more application specific integrated circuits, programmable gatearrays, programmable array logic components, or any other device ordevices that may be configured to process electronic signals. It willfurther be appreciated that a realization of the processes or devicesdescribed above may include computer-executable code created using astructured programming language such as C, an object orientedprogramming language such as C++, or any other high-level or low-levelprogramming language (including assembly languages, hardware descriptionlanguages, and database programming languages and technologies) that maybe stored, compiled or interpreted to run on one of the above devices,as well as heterogeneous combinations of processors, processorarchitectures, or combinations of different hardware and software. Atthe same time, processing may be distributed across devices such as thevarious systems described above, or all of the functionality may beintegrated into a dedicated, standalone device. All such permutationsand combinations are intended to fall within the scope of the presentdisclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps of the control systems described above. The code may be storedin a non-transitory fashion in a computer memory, which may be a memoryfrom which the program executes (such as random access memory associatedwith a processor), or a storage device such as a disk drive, flashmemory or any other optical, electromagnetic, magnetic, infrared orother device or combination of devices. In another aspect, any of thecontrol systems described above may be embodied in any suitabletransmission or propagation medium carrying computer-executable codeand/or any inputs or outputs from same.

It will be appreciated that the devices, systems, and methods describedabove are set forth by way of example and not of limitation. Numerousvariations, additions, omissions, and other modifications will beapparent to one of ordinary skill in the art. In addition, the order orpresentation of method steps in the description and drawings above isnot intended to require this order of performing the recited stepsunless a particular order is expressly required or otherwise clear fromthe context.

The method steps of the implementations described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So for example performing the step of X includes anysuitable method for causing another party such as a remote user, aremote processing resource (e.g., a server or cloud computer) or amachine to perform the step of X. Similarly, performing steps X, Y and Zmay include any method of directing or controlling any combination ofsuch other individuals or resources to perform steps X, Y and Z toobtain the benefit of such steps. Thus method steps of theimplementations described herein are intended to include any suitablemethod of causing one or more other parties or entities to perform thesteps, consistent with the patentability of the following claims, unlessa different meaning is expressly provided or otherwise clear from thecontext. Such parties or entities need not be under the direction orcontrol of any other party or entity, and need not be located within aparticular jurisdiction.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. A system comprising: a plurality of rollerspositioned relative to one another to bend a continuous material movingthrough the plurality of rollers into a curved form of the continuousmaterial having an edge-to-edge abutting relationship of a first edgeregion and a second edge region of the continuous material along aspiral joint; a first pusher actuatable to move relative to thecontinuous material to impart a first normal force on an inner surfaceof the continuous material along the spiral joint; and a second pusheractuatable to move relative to the continuous material to impart asecond normal force on an outer surface of the continuous material alongthe spiral joint.
 2. The system of claim 1, wherein at least one of theplurality of rollers is disposed along the inner surface of thecontinuous material moving through the plurality of rollers, and atleast one of the plurality of rollers is disposed along the outersurface of the continuous material moving through the plurality ofrollers.
 3. The system of claim 1, wherein the first pusher is biased ina direction into contact with the inner surface of the continuousmaterial along the spiral joint.
 4. The system of claim 1, wherein thesecond pusher is positioned relative to the plurality of rollers withthe second pusher supporting a portion of the weight of the continuousmaterial along the spiral joint.
 5. The system of claim 1, wherein thefirst pusher is positionable in rolling contact with the inner surfaceof the continuous material.
 6. The system of claim 5, wherein the secondpusher is positionable in rolling contact with the outer surface of thecontinuous material.
 7. The system of claim 1, wherein the first normalforce impartable by the first pusher is opposite the second normal forceimpartable by the second pusher.
 8. The system of claim 1, wherein thefirst pusher and the second pusher are each independently actuatablerelative to the continuous material.
 9. The system of claim 1, whereinthe first pusher is positioned relative to the plurality of rollers toimpart the first normal force proximate to a location where the firstedge region and the second edge region of the continuous materialconverge in the edge-to-edge abutting relationship.
 10. The system ofclaim 9, wherein the second pusher is positioned relative to theplurality of rollers to impart the second normal force proximate to thelocation where the first edge region and the second edge region of thecontinuous material converge in the edge-to-edge abutting relationship.11. A conical segment comprising: a continuous material in a curved formhaving an edge-to-edge abutting relationship of a first edge region anda second edge region of the continuous material along a spiral joint;and a first set of tick marks along the first edge region; and a secondset of tick marks along the second edge region, each tick mark in thefirst set of tick marks along the first edge region aligned with arespective tick mark in the second set of tick marks along the secondedge region to within a predetermined tolerance.
 12. The conical segmentof claim 11, wherein the spiral joint extends circumferentially about alongitudinal axis defined by the curved form of the continuous material.13. The conical segment of claim 12, wherein a radial distance from thelongitudinal axis to an inner surface of the curved form of thecontinuous material varies monotonically such that the conical segmentis tapered.
 14. The conical segment of claim 12, wherein a radialdistance from the longitudinal axis to an inner surface of the curvedform of the continuous material is substantially constant such that theconical segment is cylindrical.
 15. The conical segment of claim 11,wherein the first edge region and the second edge region of thecontinuous material are welded to one another along the spiral joint.